How to convert a text object directly to an ngon?
No. But there is another way to achieve it.


Select the mesh and hit Spacebar to invoke the function search menu. 
Search for limited dissolve and initiate it. You can change the parameters by hitting F6.




Also note:


After you do a limited dissolve there may still be some manual cleaning up to do.
Limited dissolve is also in the Delete menu accessible with X and Delete 
Limited dissolve is the same as the Planar setting in the Decimate modifier, so this can be done non-destructively
Blender does not support N-gons with holes in them. you will have to have a split along it somewhere.
If the n-gon is not co-planar you may see artifacts.